PROJECT SUMMARY/ABSTRACT (from parent grant) The morbidity and cost to society from childhood viral respiratory illnesses (VRI) is staggering, and allergic respiratory disease is rampant. In the search for prevention for these common and important diseases, perhaps the solutions are on the farm. Preliminary results from the Wisconsin Infant Study Cohort (WISC) demonstrate that children raised on farms have reduced VRI and atopic dermatitis, and distinct innate immune cell maturation trajectories in early life. Furthermore, in our preliminary studies mononuclear cells from Amish newborns (high microbial exposure, low rates of allergy) had a more mature phenotype and enhanced antiviral responses compared to WISC newborns. Collectively, these findings support our central hypothesis: farm- related microbial exposures are associated with increased immune cell maturation, decreased viral respiratory illness severity, and decreased allergic sensitization. To address this hypothesis, we will enlist our currently enrolled 204 WISC participants (93 farm, 111 non-farm), and enroll additional Amish, WISC farm, and WISC non-farm families (50/group). Our study has three aims that employ cutting-edge technologies and leverage our investigative team's extensive experience with farm medicine, birth cohorts, respiratory virology and immune development in children. Aim 1: To characterize how farm-related exposures relate to immune development in early life. We hypothesize that farm-related microbial exposures will prompt increased innate immune cell maturation and function in early life, including enhanced anti-inflammatory mechanisms. In these studies, we will identify farming and microbial effects on immune development of key cells (epithelial cell, plasmacytoid dendritic cell, neutrophil, Tregulatory cells) in the mucosal response to viruses and allergens. Aim 2: To determine how farm exposures affect the burden of VRI and rates of allergic diseases. We hypothesize that farm-exposed infants have reduced VRI burden and reduced sensitization to common environmental allergens. In these studies, we will use viral diagnostics to determine infections and illnesses, and measure specific IgE to aeroallergens. Aim 3: To define group-specific associations between farm-related environmental and lifestyle factors, microbial exposure and colonization (nasopharyngeal and stool), immune development, and clinical outcomes (respiratory illness burden and rates of AD and allergic sensitization). We hypothesize that house dust from farm homes, particularly Amish households, has more diverse environmental microbiota communities, more diverse microbial colonization of the nasopharynx and gut, and improved respiratory health outcomes. In these studies, microbial genomics will be used to identify bacteria and fungi in household dust, nasopharynx, and gut samples, and we will analyze relationships with patterns of immune development, VRI, and allergy. Completion of these studies will lead to development of novel strategies for enhancing immune development in early life to achieve primary prevention of VRI and allergic diseases.